Conventional tow trucks are designed to lift and tow a vehicle (e.g., an automobile) in a known manner. The disadvantage of a conventional tow truck is that it is specialized only for towing vehicles. Instead of tow trucks, specialized vehicles, such as a tractor trailer, are used to pull trailers for purposes such as transport of goods and other items. These specialized vehicles have a device known as a “fifth wheel” to permit coupling to a trailer in a conventional fashion. The trailer is equipped with a kingpin that engages with the fifth wheel. In normal operation, a significant downward force is applied to the fifth wheel by the weight of the trailer under tow and the contents, if any, of the trailer.
Past attempts have been made to provide a towing vehicle that is capable of operation as a normal tow truck (i.e., lifting and towing a vehicle) as well as operation with a fifth wheel. Such devices are disclosed by way of example in U.S. Pat. Nos. 5,823,735 and 6,036,428. In those references, a towing adapter is attached to the fifth wheel of the tow vehicle. That is, an adapter is mounted on the tow vehicle and coupled to the tow vehicle's fifth wheel to permit the tow vehicle to operate as a conventional tow truck. This technique allows the tow vehicle to be used both for conventional towing and for towing a trailer via the fifth wheel.
However, because of the position of the kingpin in devices disclosed in the noted patents, a mechanism needs to be implemented to prevent upward force from being applied to the fifth wheel. As a result, some of the disclosed devices include link members coupled between the towing frame and the vehicle frame to resist upward force of the kingpin with respect to the fifth wheel. In some embodiments the link members are made from chains and binders. When the frame twists or moves from side to side, the link members on one side tighten and the link members on the other side slack. The side to side movement results in the chains used as the link members breaking.
It is with respect to these and other considerations that embodiments of the present invention have been made. Also, although relatively specific problems have been discussed, it should be understood that embodiments of the present invention should not be limited to solving the specific problems identified in the background.